Monolithic composite membranes with continuous ionomer phases

Abstract

To provide an integral composite membrane with a continuous ionomer phase.SOLUTION: There are provided composite membranes having a microporous polymer structure, and an ion exchange material forming a continuous ionomer phase within the composite membrane. The continuous ionomer phase refers to absence of any internal interfaces in a layer of ionomer or between any number of layers coatings of the ion exchange material provided on top of one another. The composite membrane exhibits a haze change of 0% or less after being subjected to a blister test procedure. No bubbles or blisters are formed on the composite membrane after the blister test procedure. A haze value of the composite membrane is between 5% and 95%, between 10% and 90% or between 20% and 85%. The composite membrane may have a thickness of more than 17 microns at 0% relative humidity.SELECTED DRAWING: None

Description

[Technical Field]

[0001] FIELD OF THE INVENTION The present invention relates to monolithic composite membranes, and in particular to composite membranes having a continuous ionomer phase. [Background technology]

[0002] Background of the Invention Composite membranes, such as anionic, cationic, and amphoteric composite membranes, are used in a variety of applications. For example, composite membranes are components of polymer electrolyte fuel cells, where the composite membrane is positioned between the cathode and anode, allowing protons formed near the catalyst in the hydrogen electrode to be transported to the oxygen electrode, thereby allowing electrical current to be extracted from the polymer electrolyte fuel cell. These polymer electrolyte fuel cells are particularly advantageous because they operate at lower temperatures than other fuel cells. Additionally, these polymer electrolyte fuel cells do not contain the corrosive acids found in phosphoric acid fuel cells.

[0003] The composite membranes can also be used in electrochemical devices to separate liquids contained within electrochemical devices such as electrolysis cells or flow batteries, e.g., redox flow batteries. Flow batteries are charged and discharged by reversible reduction-oxidation reactions between the battery's two liquid electrolytes. Ion exchange (i.e., providing electrical current flow) occurs across the composite membrane while the two liquid electrolytes circulate through their respective spaces within the flow battery. Flow batteries are scalable systems that can operate under a wide range of conditions. For example, flow batteries can be integrated into smart grids and are advantageous for storing energy from wind or solar power plants. Flow batteries are further characterized by a long lifespan in the range of several years, simple maintenance, and overall energy efficiency.

[0004] Composite membranes incorporated into fuel cells, as well as those used in redox flow batteries, chloralkali electrolysis cells, water electrolysis, diffusion dialysis, electrodialysis, pervaporation, and vapor permeation applications, typically contain ionomer films with a discontinuous ionomer phase constructed from multiple coatings of ionomer. However, these ionomer film composite membranes can suffer from premature structural failure in flow battery applications. The primary failure mode of these ionomer film composite membranes during flow battery operation is the formation of bubbles or blisters within the ionomer layers or between multiple ionomer coatings within the membrane. Therefore, there is a need for improved composite membranes with a continuous ionomer phase, high ionic conductivity, low species crossover, high mechanical strength, and low in-plane swelling. Summary of the Invention

[0005] Summary of the Invention In one embodiment, the present invention relates to a composite membrane for a redox flow battery. The composite membrane comprises a microporous polymer structure and an ion exchange material at least partially embedded within the microporous polymer structure, occluding at least a portion of the microporous polymer structure. The ion exchange material forms a continuous ionomer phase within the composite membrane. The composite membrane exhibits a haze change of 0% or less after being subjected to a blister test procedure. The blister test procedure includes, in step 1, immersing the composite membrane in a 6 mol / L aqueous sulfuric acid solution at 80°C for 3 minutes; in step 2, removing the composite membrane from the aqueous sulfuric acid solution; in step 3, immersing the composite membrane in deionized water at ambient conditions for 1 minute; in step 4, removing the composite membrane from the deionized water; repeating the cycle consisting of steps 1-4 at least twice in succession; in step 5, drying the composite membrane at ambient conditions; and in step 6, counting the number of bubbles or blisters formed on the composite membrane. According to various embodiments, after the blister test procedure, no bubbles or blisters form on the composite film (i.e., zero bubbles or blisters are counted on the composite film). In some embodiments, the haze value of the composite film is between 5% and 95%, between 10% and 90%, or between 20% and 85%.

[0006] In some embodiments, the composite membrane comprises a single coating of ion exchange material. The composite membrane can have a thickness of 7-100 microns at 0% relative humidity, 17-50 microns at 0% relative humidity, or 25-40 microns at 0% relative humidity. Composite membranes according to various embodiments can have a thickness greater than 17 microns at 0% relative humidity.

[0007] In some embodiments, the composite membrane comprises multiple coatings of ion exchange material. In such embodiments, a first coating of ion exchange material is formed on a second coating of ion exchange material without subjecting the second coating to a drying step. The composite membrane can have a thickness of 10 to 150 microns at 0% relative humidity, 15 to 80 microns at 0% relative humidity, or 20 to 60 microns at 0% relative humidity.

[0008] According to various embodiments, the ion exchange material can have a molecular weight of 500 to 2000 g / mol equivalent, 700 to 1500 g / mol equivalent, or 900 to 1200 g / mol equivalent, or 810 to 1100 g / mol equivalent.

[0009] According to various embodiments, the composite membrane further comprises an additional layer of ion exchange material provided on the bottom surface of the composite membrane. In some embodiments, the microporous polymer structure comprises at least two microporous polymer layers. In some embodiments, the composite membrane comprises multiple ion exchange materials in the form of a mixture of ion exchange materials. In yet other embodiments, the composite membrane comprises multiple layers of ion exchange material, with the layers of ion exchange material being formed from the same ion exchange material or different ion exchange materials.

[0010] In another embodiment, the present invention relates to a composite membrane for a redox flow battery. The composite membrane includes a microporous polymer structure and an ion exchange material at least partially embedded within the microporous polymer structure, rendering at least a portion of the microporous polymer structure occlusive. The ion exchange material forms a continuous ionomer phase within the composite membrane. The composite membrane has a thickness greater than 17 microns at 0% relative humidity. For example, the composite membrane can have a thickness of 7-100 microns at 0% relative humidity, 17-50 microns at 0% relative humidity, or 25-40 microns at 0% relative humidity.

[0011] In another embodiment, the present invention relates to a composite membrane for a redox flow battery. The composite membrane comprises a microporous polymer structure and an ion exchange material at least partially embedded within the microporous polymer structure, rendering at least a portion of the microporous polymer structure occlusive. The ion exchange material forms a continuous ionomer phase within the composite membrane. The composite membrane has a thickness greater than 17 microns at 0% relative humidity. For example, the composite membrane can have a thickness of 7 to 100 microns at 0% relative humidity, 17 to 50 microns at 0% relative humidity, or 25 to 40 microns at 0% relative humidity. The composite membrane exhibits a haze change of 0% or less after being subjected to a blister test procedure. That is, the haze value of the composite membrane remains the same or decreases after being subjected to the blister test procedure. According to various embodiments, the haze value of the composite membrane is 5% to 95%, 10% to 90%, or 20% to 85%.

[0012] In another embodiment, a method for forming the composite membrane described above is provided. The method includes providing a support layer and applying an ion exchange material to the support layer in one step. The method further includes obtaining a microporous polymer structure comprising at least one microporous polymer layer. The method further includes laminating the at least one microporous polymer layer to the ion exchange material to form an impregnated microporous polymer structure having a continuous ionomer phase. The impregnated microporous polymer structure is then dried and thermally annealed to form the composite membrane.

[0013] In another embodiment, a flow battery is provided that includes the composite membrane described above. The flow battery can include a cathode reservoir containing a positive electrolyte fluid, an anode reservoir containing a negative electrolyte fluid, and an exchange region that includes the composite membrane described above disposed between a first side having a positive electrode and a second side having a negative electrode. The cathode reservoir is connected to the first side of the exchange region via a first pump, and the anode reservoir is connected to the second side of the exchange region via a second pump.

[0014] In another embodiment, a composite membrane is provided, the composite membrane being prepared by a process comprising obtaining an untreated microporous polymer structure, applying an impregnating agent solution comprising an ion exchange material to the untreated microporous polymer structure to form a treated microporous polymer structure having a continuous ionomer phase, and drying and thermally annealing the treated microporous polymer structure to form a composite membrane, wherein the ion exchange material forms a continuous ionomer phase within the composite membrane, and the composite membrane exhibits a haze change of 0% or less after being subjected to a blister test procedure.

[0015] Other aspects and variations of the invention will become apparent in the discussion that follows. [Brief explanation of the drawings]

[0016] BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood in view of the following non-limiting figures.

[0017] [Figure 1] 1A-1C show photomicrographs of cross sections of composite membranes containing bubbles or blisters.

[0018] [Figure 2] 2A and 2B show photomicrographs of a cross section of a composite membrane having a discontinuous ionomer phase containing bubbles or blisters within the interface between the two ionomers.

[0019] [Figure 3A]FIG. 3A shows a cross-sectional side view of a composite membrane according to some embodiments of the present invention.

[0020] [Figure 3B] FIG. 3B shows an exemplary flow diagram of a method for constructing an exemplary composite membrane according to some embodiments of the present invention. [Figure 3C] FIG. 3C shows an exemplary flow diagram of a method for constructing an exemplary composite membrane according to some embodiments of the present invention. [Figure 3D] FIG. 3D shows an exemplary flow diagram of a method for constructing an exemplary composite membrane according to some embodiments of the present invention.

[0021] [Figure 3E] FIG. 3E shows a micrograph of a composite membrane with a porous substrate and a continuous ionomer phase characterized by nodes interconnected by fibrils, according to various embodiments. [Figure 3F] FIG. 3F shows a micrograph of a composite membrane with a porous substrate and a continuous ionomer phase characterized by nodes interconnected by fibrils, according to various embodiments.

[0022] [Figure 4] FIG. 4 shows a schematic diagram of a flow battery including a composite membrane according to some embodiments of the present invention.

[0023] [Figure 5] 5A-5B show schematic diagrams of a haze test apparatus for measuring the total light transmittance of composite films according to some embodiments of the present invention.

[0024] [Figure 6] 6A-6B show an exemplary composite membrane prepared in accordance with an embodiment of the present invention and a conventional ion exchange membrane before and after blister testing, respectively; and

[0025] [Figure 7]7A-7C show samples of composite membranes prepared according to embodiments of the present invention after blister testing according to some embodiments of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] Detailed Description of the Invention I. Introduction In one embodiment, the present invention is directed to a composite membrane (e.g., an ionomer film composite membrane) comprising a porous substrate with an impregnating agent comprising an ion exchange material. However, one problem associated with conventional ionomer film composite membranes is their reduced ability to maintain structural integrity, particularly when used in flow batteries. For example, it has been discovered that bubbles or blisters can form in the ionomer film composite membrane within the membrane at weak internal interfaces within the ionomer layer or between multiple ionomer coatings resulting from the conventional multi-pass coating process used to manufacture the ionomer film composite membrane. Figures 1A-1C show micrographs of a conventional ionomer film composite membrane 100 having bubbles or blisters 110 at weak internal interfaces 120 between multiple ionomer coatings 130.

[0027] A conventional multi-pass coating process for making ionomer film composite membranes involves a first-pass ionomer coating, which involves contacting a porous substrate, such as expanded polytetrafluoroethylene (ePTFE), with an impregnating agent, such as a perfluorosulfonic acid polymer, to form a first-pass ionomer. The first-pass ionomer is then heated in an oven to dry the porous substrate containing the impregnating agent and thermally anneal. A second-pass ionomer coating is then applied to the already dried first-pass ionomer, contacted with the porous substrate to form a second-pass ionomer, and the second-pass ionomer is dried. Optionally, additional passes of ionomer coatings may be superimposed, contacted with the porous substrate, dried, and annealed. The resulting structure is characterized by a discontinuous ionomer phase with internal interfaces between each ionomer, e.g., between the first-pass ionomer and the second-pass ionomer. 2A-2B show photomicrographs of a conventional ionomer film composite membrane 200 having a discontinuous ionomer phase 210 with cells or blisters 220 formed at the internal interfaces 230 between each ionomer 240. Fibril-like structures 250 are observed within the cells or blisters 220.

[0028] Without being bound by theory, it is possible that the liquid electrolyte used in flow batteries is attracted to the internal interfaces within the ionomer layers or between the ionomers, thereby generating an osmotic pressure gradient within the composite membrane during operation of the flow battery. The osmotic pressure gradient acts as a driving force for drawing water into the internal interfaces during operation of the flow battery. The hydrodynamic expansion forces associated with water being drawn into the internal interfaces result in the formation of bubbles or blisters between the ionomers.

[0029] To address these concerns, in one embodiment, the present invention is further directed to a composite membrane having a continuous ionomer phase. As used herein, "continuous ionomer phase" refers to a porous substrate and / or any number of superimposed layers or coatings of ion exchange material that do not have internal interfaces within or between layers or coatings of ionomer. An integral interface can be achieved, for example, by drying and thermally annealing the porous substrate and / or ion exchange material before applying the next layer or coating. In some embodiments, a single-pass ionomer coating process is performed as described herein to create a single-pass ionomer composite membrane having a continuous ionomer phase. Composite membranes made with a single-pass ionomer coating optionally have a thickness in the range of 7-100 microns at 0% relative humidity (RH), 17-50 microns at 0% RH, or 25-40 microns at 0% RH, and optionally have a thickness of 3 g / m 2 ~80g / m 2 of porous substrate or 5g / m 2 ~50g / m 2 of porous substrate or 10 g / m 2 ~30g / m 2 In an alternative embodiment, a multiple-pass ionomer coating process is performed as described herein without a drying step between each pass of coating to produce a multiple-pass ionomer composite membrane having a continuous ionomer phase. The multiple-pass ionomer composite membrane optionally has a thickness in the range of 10-150 microns at 0% RH, 15-80 microns at 0% RH, or 20-60 microns at 0% RH, and optionally has a thickness of 3 g / m 2 ~80g / m 2 of porous substrate or 5g / m 2 ~50g / m 2 of porous substrate or 10 g / m 2 ~30g / m 2In some embodiments, a specific equivalent weight of ion exchange material is used in an ionomer coating process, as described herein, to produce a composite membrane having a continuous ionomer phase. The ion exchange material optionally has an equivalent weight of 500 to 2000 g / mole equivalent, or 700 to 1500 g / mole equivalent, or 700 to 1200 g / mole equivalent, or 810 to 1100 g / mole equivalent. In some embodiments, a single-pass or multiple-pass ionomer coating process, as described herein, is performed without a drying step between each coating pass to produce a composite membrane having a continuous ionomer phase with a predetermined haze. The haze of the composite membrane is optionally 5% to 95%, or 10% to 90%, or 20% to 85%. The composite membrane optionally exhibits a decrease or no change in its haze value after such membrane is subjected to a blister test procedure. Thus, in one embodiment, the present invention is directed to composite membranes having a continuous ionomer phase that does not have internal interfaces within a layer of ionomer or between multiple coatings of ionomer, and that exhibit desirable high ionic conductivity, low crossover of reactive species, high mechanical strength, and low in-plane swelling properties.

[0030] Various definitions used in this disclosure are provided below.

[0031] As used herein, the terms "ionomer" and "ion exchange material" refer to cation exchange materials, anion exchange materials, or ion exchange materials containing both cation and anion exchange capabilities. Mixtures of ion exchange materials can also be used. The ion exchange materials can be perfluorinated or hydrocarbon-based. Suitable ion exchange materials include, for example, perfluorosulfonic acid polymers, perfluorocarboxylic acid polymers, perfluorophosphonic acid polymers, styrene ion exchange polymers, fluorostyrene ion exchange polymers, polyaryletherketone ion exchange polymers, polysulfone ion exchange polymers, bis(fluoroalkylsulfonyl)imides, (fluoroalkylsulfonyl)(fluorosulfonyl)imides, polyvinyl alcohol, polyethylene oxide, divinylbenzene, metal salts with or without polymers, and mixtures thereof. In an exemplary embodiment, the ion exchange material comprises a perfluorosulfonic acid (PFSA) polymer prepared by copolymerization of tetrafluoroethylene and perfluorosulfonyl vinyl ester, converted to the proton form. Of course, the suitability of a particular ion exchange material will depend in part on the application for which the composite membrane is intended. Examples of perfluorosulfonic acid polymers suitable for use in fuel cell or flow battery applications include Nafion® (El DuPont de Nemours, Inc., Wilmington, Del., US), Flemion® (Asahi Glass Co. Ltd., Tokyo, JP), and Aciplex® (Asahi Chemical Co. Ltd., Tokyo, JP), which are commercially available perfluorosulfonic acid copolymers. Other examples of perfluorosulfonic acid polymers suitable for use in fuel cell applications include perfluorinated sulfonyl (co)polymers such as those described in U.S. Pat. No. 5,463,005.

[0032] As used herein, "continuous ionomer phase" refers to an ionomer that does not have an internal interface. A continuous ionomer phase can refer to, but is not limited to, a composite membrane made with a single-pass ionomer coating. A composite membrane made with a single-pass ionomer coating can include one or more layers of material (e.g., a coating of an absorbent layer formed on a backer layer and laminated with a microporous polymer layer (e.g., an ionomer layer impregnated into a microporous polymer structure)) that are formed on top of each other, dried, and thermally annealed (e.g., cured).

[0033] As used herein, the term "microporous polymer structure" refers to a polymer matrix that supports the ion exchange material and adds structural integrity and durability to the resulting composite membrane. In an exemplary embodiment, the microporous polymer structure comprises expanded polytetrafluoroethylene having a node and fibril structure. The microporous structures described herein have pores that are invisible to the naked eye. According to various optional embodiments, the pores can have an average pore size of 0.01 to 100 microns, e.g., 0.05 to 10 microns or 0.1 to 1 micron.

[0034] In some embodiments, the microporous polymer structure is expanded polytetrafluoroethylene having an average pore size of 0.01 to 100 microns, for example, 0.05 to 10 microns or 0.1 to 1 micron.

[0035] As used herein, the interior volume of a microporous polymer structure is referred to as "substantially occluded" when said interior volume is characterized by a low volume of voids of less than 10% by volume, and has a structure that is highly impermeable to gases, with a Gurley number greater than 10,000 seconds. Conversely, the interior volume of a microporous polymer structure is referred to as "non-occluded" when said interior volume is characterized by a high volume of voids of more than 10% by volume, and has a structure that is permeable to gases, with a Gurley number less than 10,000 seconds.

[0036] In some embodiments, the microporous polymer structure is expanded polytetrafluoroethylene having an average pore size of 0.01 to 100 microns, eg, 0.05 to 10 microns or 0.1 to 1 micron, and having less than 10% voids by volume.

[0037] The appropriate microporous polymer structure depends largely on the application in which the composite membrane is used. The microporous polymer structure preferably has good mechanical properties, is chemically and thermally stable in the environment in which the composite membrane is used, and is resistant to any additives used with the ion exchange material for impregnation. Microporous polymer structures suitable for redox flow battery or fuel cell applications can include porous polymer materials. Porous polymer materials can include fluoropolymers, chlorinated polymers, hydrocarbons, polyamides, polycarbonates, polyacrylates, polysulfones, copolyetheresters, polyvinylidene fluoride, polyaryletherketones, polybenzimidazoles, poly(ethylene-co-tetrafluoroethylene), and poly(tetrafluoroethylene-co-hexafluoropropylene). In some embodiments, the microporous polymer structure includes a perfluorinated porous polymer material. The perfluorinated porous polymeric material can include polytetrafluoroethylene (PTFE), expanded polytetrafluoroethylene (ePTFE), polyvinylidene fluoride (PVDF), expanded polyvinylidene fluoride (ePVDF), expanded poly(ethylene-co-tetrafluoroethylene) (eEPTFE), or mixtures thereof. In some embodiments, the microporous polymeric structure comprises a hydrocarbon material. The hydrocarbon material can include polyethylene, expanded polyethylene, polypropylene, expanded polypropylene, polystyrene, or mixtures thereof. An example of a perfluorinated porous polymeric material suitable for use in redox flow battery or fuel cell applications includes ePTFE manufactured according to the teachings of U.S. Pat. No. 8,757,395, which is incorporated herein by reference in its entirety and is commercially available in various forms from W.L. Gore & Associates, Inc. of Elkton, MD.

[0038] II. Composite membrane Composite membranes having either a continuous ionomer phase or a discontinuous ionomer phase have a certain haze. Haze refers to the wide-angle scattering of light by a composite membrane, resulting in a loss of optical contrast that allows objects to be seen when viewed through the composite membrane. Haze can be measured with a haze meter or a transparency meter, as described in detail herein. Composite membranes having a continuous ionomer phase do not blister. Therefore, the haze of a composite membrane having a continuous ionomer phase does not change after blister testing or continuous operation in a flow battery. On the other hand, composite membranes having a discontinuous ionomer phase (i.e., composite membranes without a continuous ionomer phase) do blister. Therefore, the haze of a composite membrane having a discontinuous ionomer phase changes after blister testing or continuous operation in a flow battery. The haze of a composite membrane having a continuous ionomer phase is similar to the haze of a composite membrane without a continuous ionomer phase before blister testing. However, the haze of the composite membrane with a continuous ionomer phase is different from the haze of the composite membrane without a continuous ionomer phase after the blister test.

[0039] Composite membranes having either a continuous ionomer phase or a discontinuous ionomer phase also have a predetermined bubble or blister density that can be measured after the membrane has been continuously used for a predetermined period of time in a flow battery or after being subjected to the blister test procedure described in detail herein, where the bubble or blister area is measured as the ratio of the area of ​​the composite membrane to the area of ​​the bubbles or blisters in the composite membrane.

[0040] In some embodiments, a composite membrane formed via a single pass of ionomer coating and having a continuous ionomer phase after 10 days of continuous use in a flow battery has a predetermined bubble or blister density of less than 0.3%, less than 0.2%, less than 0.1%, or 0%. In alternative embodiments, a composite membrane formed via multiple passes of ionomer coating without a drying step between each pass of coating and having a continuous ionomer phase after 10 days of continuous use in a flow battery has a bubble or blister area of ​​less than 0.3%, less than 0.2%, less than 0.1%, or 0%. In other embodiments, a composite membrane formed via a single pass of ionomer coating and having a continuous ionomer phase after undergoing a blister testing procedure has a bubble or blister area of ​​less than 0.3%, less than 0.2%, less than 0.1%, or 0%. In alternative embodiments, the air bubble or blister area of ​​the continuous ionomer phase formed via multiple passes of ionomer coating without a drying step between each coating pass and after undergoing the blister test procedure is less than 0.3%, less than 0.2%, less than 0.1%, or 0%. In some embodiments, the change in haze of a composite membrane having a continuous ionomer phase formed via a single pass of ionomer coating and after undergoing the blister test procedure is 0% or less, 0% to -60%, 0% to -45%, 0% to -30%, or 0% to -21%. In alternative embodiments, the change in haze of a composite membrane having a continuous ionomer phase formed via multiple passes of ionomer coating without a drying step between each coating pass and after undergoing the blister test is 0% or less, 0% to -60%, 0% to -45%, 0% to -30%, or 0% to -21%.

[0041] a. Composite membrane with a continuous ionomer phase As described above, composite membranes according to various embodiments have a continuous ionomer phase. As shown in FIG. 3A , a composite membrane is provided that includes a microporous substrate 306 and an impregnating agent comprising an ion exchange material or ion exchange resin 304 characterized by a continuous ionomer phase 350 (i.e., no interfaces between ionomer coatings). The porous substrate 306 is a membrane defined by a thickness of less than 0.4 mm (400 microns). The ion exchange resin 304 substantially impregnates the porous substrate 306 so as to render the interior volume substantially occlusive. For example, substantial occlusion would occur by filling more than 90% of the interior volume of the porous substrate 306 with the ion exchange resin 304.

[0042] The composite membranes of the present disclosure can be used in a variety of applications. In some embodiments, the composite membranes of the present disclosure can be used in industrial electrochemistry and other electrochemical applications, such as polar-based chemical separations, pervaporation, gas separation, dialysis separation, chloralkali electrolysis, and can be used as superacid catalysts or as media in enzyme immobilization. In preferred embodiments, the composite membranes of the present disclosure can be used in electrochemical applications to separate liquids contained within electrochemical devices. In preferred embodiments, the composite membranes of the present disclosure can be used in fuel cells. In another preferred embodiment, the composite membranes of the present disclosure can be used in water electrolysis cells, water electrolyzers. In yet another preferred embodiment, the composite membranes of the present disclosure can be used in flow batteries, such as redox flow batteries.

[0043] The impregnating agent comprises an ion exchange material or resin 304. The ion exchange material or resin 304 may be a cation exchange material, an anion exchange material, or an ion exchange material containing both cation and anion exchange capacity. Mixtures of ion exchange materials may also be used as the impregnating agent.

[0044] Optionally, the impregnating solution further comprises a surfactant. Surfactants may be used in conjunction with the ion exchange material to ensure impregnation of the interior volume of the porous substrate. Surfactants or surface-active agents having hydrophobic and hydrophilic moieties may be utilized. Preferred surfactants have a molecular weight greater than 100 and may be classified as anionic, nonionic, or amphoteric, which may be hydrocarbon or fluorocarbon-based, such as Merpol®, a hydrocarbon-based surfactant, or Zonyl®, a fluorocarbon-based surfactant, both commercially available from EI DuPont de Nemours, Inc., Wilmington, DE.

[0045] In various embodiments, the surfactant is octylphenoxypolyethoxyethanol, a non-ionic material, having the following chemical structure: [ka] (where x=10 (average)). This is known as Triton X-100 and is commercially available from Rohm & Haas of Philadelphia, Pa.

[0046] The impregnating agent can further contain other components as desired. For example, the impregnating agent can include an electrocatalyst composition. Suitable catalyst compositions include unsupported and supported catalysts containing noble metals, transition metals, their oxides, their alloys, and mixtures thereof. The presence of an electrocatalyst in the ion-exchange layer of the composite membrane may be desirable, for example, to reduce crossover of reactants such as methanol in direct methanol fuel cell applications. Additionally, the electrocatalyst can provide more effective ionomer-electrocatalyst interactions, thereby promoting the oxidation and reduction of reactant gases.

[0047] The impregnating agent may further comprise an electrochemically inert material that promotes water retention within the composite membrane under normal operating conditions. Polymeric, non-polymeric, or hydrogel materials may be suitable. For example, the impregnating agent may further comprise particulate silica and / or fibrous silica, as described in U.S. Pat. No. 5,523,181 (incorporated herein by reference), or a hydrogel containing silicon oxide, as described in Chemistry of Materials, Vol. 7, pp. 2259-2268 (1995). Other suitable such materials will be apparent to those skilled in the art.

[0048] The impregnating agent can further include a compatible mixture of non-ionic polymers, such as, for example, polyaryletherketones or polysulfones. Having a non-ionic polymer in the impregnating agent can be advantageous in some applications. For example, a non-ionic polymer in the impregnating agent can reduce the amount of methanol crossover in direct methanol fuel cells.

[0049] In embodiments in which a polymeric composition is used, the impregnating agent is typically introduced into the porous substrate via an impregnating agent solution comprising the impregnating agent in a suitable solvent. The choice of solvent will depend, in part, on both the composition of the impregnating agent and the composition of the porous substrate. Suitable solvents include, for example, water, ethanol, propanol, butanol, methanol, ketones, carbonates, tetrahydrofuran, acetonitrile, N,N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, N,N-dimethylacetamide, and mixtures thereof. As used herein, "solvent" refers to any suitable solvent or mixture of solvents.

[0050] Alternatively, the ion exchange material may comprise one or more monomers or oligomers that can be impregnated into the porous substrate and subsequently polymerized or otherwise chemically bonded. Thus, as used herein, "impregnating solution" includes ion exchange monomers, oligomers, polymers, and / or mixtures thereof in a solvent, as well as pure ion exchange material monomers and / or oligomers. It should be noted that if the impregnating solution contains additional components separate from the ion exchange material, those components need not be dissolved in the liquid phase. In this case, the impregnating solution may be a dispersion.

[0051] In one embodiment, a composite membrane for a redox flow battery can include expanded polytetrafluoroethylene having an average pore size of 0.01 to 100 microns and a perfluorosulfonic acid resin having an EW of 810 to 1100 g / mol acid equivalent, at least partially embedded within the microporous polymer structure and occluding at least a portion of the microporous polymer structure. The perfluorosulfonic acid resin forms a continuous ionomer phase within the composite membrane. The composite membrane exhibits a haze change of 0% or less after undergoing a blister test procedure.

[0052] b. Process for preparing composite membranes 3B-3C show exemplary flow diagrams of processes 340 and 360 for constructing exemplary composite membranes 300 and 380, respectively, according to various aspects of the present disclosure. The flow diagrams illustrate the architecture, functionality, and operation of possible implementations of systems and methods according to various embodiments of the present disclosure. In some alternative embodiments, where it makes logical sense to do so, the functions shown in each block may differ from the order shown in the figures. For example, two blocks shown in succession may, in fact, be performed substantially simultaneously, or the blocks may sometimes be performed in the reverse order, depending on the functionality, process, or end product involved.

[0053] 3B, an exemplary flow diagram of process 340 illustrates a method for forming a composite material 300 having a fully imbibed microporous polymer structure 307, an additional layer of ion exchange material 305, and an uncoated non-occlusive layer 309. Process 340 includes providing a support structure, such as a backer 302.

[0054] Suitable support structures can include, for example, woven materials, which can include scrims made from woven fibers of expanded porous polytetrafluoroethylene, webs made from extruded or oriented polypropylene or polypropylene netting, commercially available from Conwed, Inc. of Minneapolis, Minn., and woven polypropylene and polyester materials available from Tetko Inc. of Briarcliff Manor, N.Y. Suitable nonwoven materials can include, for example, spunbond polypropylene from Reemay Inc. of Old Hickory, Tenn. In other embodiments, the support structure can comprise a web of polyethylene ("PE"), polystyrene ("PS"), cyclic olefin copolymer ("COC"), cyclic olefin polymer ("COP"), fluorinated ethylene propylene ("FEP"), perfluoroalkoxyalkane ("PFA"), ethylene tetrafluoroethylene ("ETFE"), polyvinylidene fluoride ("PVDF"), polyetherimide ("PEI"), polysulfone ("PSU"), polyethersulfone ("PES"), polyphenylene oxide ("PPO"), polyphenylether ("PPE"), polymethylpentene ("PMP"), polyethylene terephthalate ("PET"), or polycarbonate ("PC"). In some embodiments, the support structure also includes a protective layer that can include polyethylene (PE), polystyrene ("PS"), cyclic olefin copolymer ("COC"), cyclic olefin polymer ("COP"), fluorinated ethylene propylene ("FEP"), perfluoroalkoxyalkane ("PFA"), ethylene tetrafluoroethylene ("ETFE"), polyvinylidene fluoride ("PVDF"), polyetherimide ("PEI"), polysulfone ("PSU"), polyethersulfone ("PES"), polyphenylene oxide ("PPO"), polyphenylether ("PPE"), polymethylpentene ("PMP"), polyethylene terephthalate ("PET"), or polycarbonate ("PC").

[0055] In yet another embodiment, the support structure can optionally include a reflective layer comprising a metal substrate (e.g., an aluminum substrate). The specific metal selected can vary widely, so long as it is reflective. A non-limiting list of exemplary metals includes aluminum, beryllium, cerium, chromium, copper, germanium, gold, hafnium, manganese, molybdenum, nickel, platinum, rhodium, silver, tantalum, titanium, tungsten, zinc, or alloys such as Inconel or bronze. The reflective layer can optionally include a mixture or alloy of two or more metals, and optionally includes a mixture or alloy of two or more of the above metals. The reflective layer can optionally include a highly reflective polymer multilayer film, such as Vikuiti™ Enhanced Specular Reflector available from 3M. In yet another example, the reflective layer can optionally include a highly reflective non-metallic inorganic dielectric multilayer film, including materials such as magnesium fluoride, calcium fluoride, titanium dioxide, and silicon dioxide.

[0056] In step 342, the first ion exchange material is applied to the support structure as a layer of controlled thickness in a single-pass or multiple-pass ionomer coating technique, including forward roll coating, reverse roll coating, gravure coating, doctor coating, kiss coating, slot die coating, slide die coating, as well as dipping, brushing, painting, and spraying. The first ion exchange material can be prepared by dissolving the ion exchange material in a solvent. The first ion exchange material can include an ion exchange material and a solvent, and optionally, additional components such as a surfactant. In some embodiments, the ion exchange material is a cation exchange material, an anion exchange material, or an ion exchange material containing both cation and anion exchange capabilities. The choice of solvent can depend in part on both the composition of the ionomer and the composition of the porous substrate.

[0057] In step 344, the green microporous polymer structure is laminated onto at least a portion of the first ion exchange material by any conventional technique, such as, for example, hot roll lamination, ultrasonic lamination, adhesive lamination, contact lamination, or forced hot air lamination, so long as the technique does not destroy the integrity of the green microporous polymer structure. In some embodiments, the green microporous polymer structure comprises ePTFE having a microporous polymer structure. The microporous polymer structure can be characterized by a uniform structure and composition throughout its thickness. In other aspects, the structure and composition of the microporous polymer structure can vary throughout its thickness. The prepared or resulting microporous polymer structure can have a thickness of less than 400 microns at 0% relative humidity, e.g., a thickness of 1 micron to 400 microns. The green microporous polymer structure has a mass per unit area of ​​0.05 g / m at 0% relative humidity. 2 can exceed, for example, 0.3 g / m 2 ~80g / m 2 It can be.

[0058] For example, a carrier support, such as a backer, can be continuously fed from a roller unwinding station through registration and tension rollers to a coating station. The ion exchange material can be applied as a layer of controlled thickness onto the surface of the carrier support (backer) by a suitable coating means, such as a doctor blade. An untreated microporous polymer structure can be continuously fed from the roller unwinding station to the registration rollers, where it contacts the coated carrier support and becomes impregnated with the ion exchange material. Alternatively, the carrier support can be eliminated, and a layer of ion exchange material can be applied directly to the untreated microporous polymer structure.

[0059] In step 346, the treated microporous polymer structure is placed in an oven to dry and thermally anneal to complete the construction of the composite membrane. The oven temperature can be greater than 60°C, e.g., 60°C to 220°C or 150°C to 200°C. Drying and thermally annealing the treated microporous polymer structure in the oven ensures adhesion of the ion exchange material to the internal membrane surface and, optionally, to the external membrane surface, e.g., to the fibrils and / or nodes of the microporous polymer structure. The resulting dried and annealed composite membrane 300 can have a thickness greater than 17 microns, e.g., 17 microns to 100 microns at 0% relative humidity. The composite membrane mass can be 30 g / m 2 It may be larger, for example 30 g / m at 0% relative humidity. 2 ~200g / m 2 It can be.

[0060] 3C, an exemplary flow diagram of process 360 illustrates a method for forming a composite material 380 having a fully imbibed microporous polymer structure 307, an additional layer of ion exchange material 305, and a partially coated non-occlusive layer 319. Process 360, similar to process 340, includes providing a support structure (e.g., backer) 302, such as a woven material.

[0061] In step 362, the first ion exchange material is applied to a support structure (backer) as a layer of controlled thickness, similar to step 342 of process 340. A description of step 362 will be omitted here, as it is identical to step 342 of process 340 described above.

[0062] In step 364, the green microporous polymer structure is laminated onto the first portion of the first ion exchange material by any conventional technique, such as hot roll lamination, ultrasonic lamination, adhesive lamination, contact lamination, or forced hot air lamination, so long as the technique does not compromise the integrity of the green microporous polymer structure. In some embodiments, the green microporous polymer structure comprises ePTFE having a microporous polymer structure. The microporous polymer structure can be characterized by a uniform structure and composition throughout its thickness. In other aspects, the structure and composition of the microporous polymer structure can vary throughout its thickness.

[0063] After lamination, a touch roll 310 can be used to coat the top of the microporous polymer structure with, for example, an ionomer coating.

[0064] Step 366 is similar to step 346 of process 340. Therefore, the description of step 366 is omitted here. The prepared or obtained microporous polymer structure, after drying and annealing, can have a thickness of more than 17 microns at 0% relative humidity, for example, a thickness of 17 microns to 100 microns. The mass of the composite membrane can be 30 g / m at 0% relative humidity. 2 It may be larger, for example, 30 g / m 2 ~200g / m 2 It can be.

[0065] 3D, an exemplary flow diagram of process 320 illustrates a method for forming a composite material 321 having a fully imbibed microporous polymer structure 307 and two additional layers of ion exchange material 305. Process 320 provides a support structure (e.g., backer) 302, such as a woven material, similar to processes 340 and 360.

[0066] In step 322, the first ion exchange material is applied to a support structure (backer) as a layer of controlled thickness, similar to step 342 of process 340. A description of step 322 is omitted here, as it is identical to step 342 of process 340 above.

[0067] In step 324, the green microporous polymer structure is laminated onto the first portion of the first ion exchange material by any conventional technique, such as hot roll lamination, ultrasonic lamination, adhesive lamination, contact lamination, or forced hot air lamination, so long as the technique does not compromise the integrity of the green microporous polymer structure. In some embodiments, the green microporous polymer structure comprises ePTFE having a microporous polymer structure. The microporous polymer structure can be characterized by a uniform structure and composition throughout its thickness. In other aspects, the structure and composition of the microporous polymer structure can vary throughout its thickness.

[0068] After lamination, in step 326, a second ion exchange material 327 is applied as a layer of controlled thickness to the top surface of the microporous polymer structure using ionomer coating techniques, including forward roll coating, reverse roll coating, gravure coating, doctor coating, kiss coating, slot die coating, slide die coating, as well as dipping, brushing, painting, and spraying. The second ion exchange material can be prepared by dissolving the ion exchange material in a solvent. The second ion exchange material can include an ion exchange material and a solvent, and optionally additional components such as a surfactant. In some embodiments, the ion exchange material is a cation exchange material, an anion exchange material, or an ion exchange material containing both cation and anion exchange capabilities. The choice of solvent can depend in part on both the composition of the ionomer and the composition of the porous substrate.

[0069] Step 328 is similar to step 346 of process 340. Therefore, a description of step 328 is omitted here. The prepared or obtained composite membrane after drying and annealing can have a thickness of more than 17 microns, for example, a thickness of 17 microns to 100 microns, at 0% relative humidity. The mass of the composite membrane can be 30 g / m at 0% relative humidity. 2 It may be larger, for example, 30 g / m 2 ~200g / m 2It can be.

[0070] Processes 340, 360, and 320 can include optional steps of submerging the composite membrane and boiling the composite membrane. For example, in embodiments where a surfactant is used, the composite membrane is further treated to remove the surfactant. This is accomplished by soaking or submerging the composite membrane in a solution of, for example, water, isopropyl alcohol, hydrogen peroxide, methanol, and / or glycerin. This step removes the surfactant that was originally mixed with the ion exchange material in the solution. This soaking or submersion causes slight swelling of the composite membrane, but the ion exchange material remains within the interior volume of the porous substrate.

[0071] In the optional boiling step, the composite membrane is treated by boiling in a suitable swelling agent, preferably water, to slightly swell the composite membrane in the x, y, and z directions. The swollen composite membrane has a higher and stronger ion transport rate. Unlike membranes consisting solely of ion exchange material, the swollen composite membrane retains its mechanical integrity and dimensional stability while maintaining the desired ion transport properties. A correlation exists between the swelling agent content in the composite membrane and the transport properties of the composite membrane. The swollen composite membrane transports chemical species faster than the unswollen composite membrane.

[0072] 3B-3D, composite membranes 300, 380, 321 include a microporous polymer structure 306 and an ion exchange material (e.g., an ionomer) 304 impregnated within the microporous polymer structure 306. That is, the microporous polymer structure 306 is imbibed with the ion exchange material 304. The ion exchange material 304 can substantially impregnate the microporous polymer structure 306 such that the interior volume is substantially occlusive (i.e., the interior volume is characterized by a low volume of voids and has a structure that is highly impermeable to gases). For example, filling greater than 90% of the interior volume of the microporous polymer structure 306 with the ion exchange material 304 results in substantial occlusion, and the membrane is characterized by a Gurley number greater than 10,000 seconds. The ion exchange material 304 is firmly adhered to the interior and exterior surfaces of the microporous polymer structure 306 , for example, to the fibrils and / or nodes of the microporous polymer structure 306 , forming an absorbent layer 307 .

[0073] In some embodiments, the ion exchange material 304, in addition to being impregnated into the microporous polymer structure 306 within the absorbent layer 307, is provided as one or more additional layers 305 on one or more outer surfaces of the absorbent layer 307 (e.g., also referred to as a "butter coat (BC)").

[0074] 3B, a portion of the microporous polymer structure 306 (e.g., the top or bottom region) can include a non-occlusive (i.e., an interior volume characterized by a high volume of voids and having a structure that is highly permeable to gases) layer 309, which is free or substantially free of ion exchange material 304. The location of the non-occlusive layer 309 is not limited to the top region of the microporous polymer structure 306. As noted above, the non-occlusive layer 309 is not provided on the bottom area 306 of the microporous polymer structure 306.

[0075] 3C, the non-occlusive layer 319 can include a small amount of ion exchange material 304 present as a thin coating of nodes and fibrils on the interior surface of the microporous polymer structure 306. However, the amount of ion exchange material 304 is not sufficient to cause the microporous polymer structure 306 to become occlusive, thereby forming the non-occlusive layer 319.

[0076] In some embodiments, the composite membrane 300, 380, 321 can be provided on a support layer 302. The support layer 302 can include a backer, for example, a peelable film such as a cycloolefin copolymer (COC) layer. In some embodiments, the composite membrane 300, 380, 321 can be peeled (or debonded) from the support layer 302 before being incorporated into a membrane electrode assembly (MEA).

[0077] 3B-3D show exemplary composite membranes 300, 380, 321 that include a single type of ion exchange material 304. However, applications are not limited to composite membranes with a single type of ion exchange material 304 or a single absorbent layer 307.

[0078] Figures 3E-3F show micrographs of composite membranes having a porous substrate characterized by nodes interconnected by fibrils and a continuous ionomer phase, according to various embodiments. As shown in Figures 3E-3F, composite membranes prepared according to aspects of the invention have a uniform thickness without internal interfaces within layers of ionomer or between multiple coatings of ionomer, and without discontinuities or pinholes on the surface. The interior volume of the composite membrane is substantially closed, such that the composite membrane is impermeable to the bulk flow of non-polar gases and liquids.

[0079] c. Preparation and application of the impregnating solution Referring back to steps 342, 362 and 322, the preparation of the impregnating solution and its application onto the support structure will now be described.

[0080] The impregnating solution is prepared by dissolving the ion exchange material in a solvent. The impregnating solution contains the ion exchange material and, optionally, other components, such as a surfactant, in a solvent. The ion exchange material can be a cation exchange material, an anion exchange material, or an ion exchange material that contains both cation and anion exchange capabilities. The choice of solvent depends, in part, on both the composition of the impregnating agent and the composition of the porous substrate.

[0081] The impregnating solution can be applied as a layer of controlled thickness to an untreated porous substrate in single-pass ionomer coating techniques, including forward roll coating, reverse roll coating, gravure coating, doctor coating, kiss coating, and dipping, brushing, painting, and spraying, as long as the solution can penetrate the interstices and internal volumes of the untreated porous substrate. Excess solution can be removed from the surface of the treated porous substrate. For example, the carrier support can be continuously fed from a roller unwinding station through alignment rollers and tension rollers to a coating station. The impregnating solution can be applied as a layer of controlled thickness to the surface of the carrier support by a suitable coating means, such as a doctor blade. The untreated porous substrate is continuously fed from a roller unwinding station to an alignment roller, which contacts the coated carrier support and impregnates it with the impregnating solution. Alternatively, the carrier support can be eliminated, and a layer of impregnating solution can be applied directly to the untreated porous substrate.

[0082] The resulting treated porous substrate or composite membrane produced by a single pass ionomer coating has a thickness in the range of 7 to 100 microns, 17 to 50 microns, or 25 to 40 microns, and optionally has a coating weight of 3 g / m 2 ~80g / m 2 or 5 g / m 2 ~50g / m 2 or 10 g / m 2 ~30g / m 2As should be understood, a single pass ionomer coating results in a composite membrane having a continuous ionomer phase with no internal interfaces in the single coating of ionomer.

[0083] In some embodiments, the impregnating solution is applied to the surface of the treated porous substrate as multiple additional layers of controlled thickness (i.e., multiple passes of ionomer) by, for example, forward roll coating, reverse roll coating, gravure coating, doctor coating, kiss coating, and similar coating techniques such as dipping, brushing, painting, and spraying. For example, the treated porous substrate can be continuously fed through registration rollers, contacted with the coated carrier support one or more additional times (multiple passes), and impregnated with the impregnating solution. Alternatively, the carrier support can be eliminated, and multiple layers of impregnating solution can be applied directly to the treated porous substrate. This process can be repeated any number of times (e.g., twice) without a drying step between each coating pass to create a treated porous substrate with multiple layers. The resulting multi-pass composite membrane has a thickness ranging from 10 to 150 microns at 0% RH, 15 to 80 microns at 0% RH, or 20 to 60 microns at 0% RH, and optionally has a coating density of 3 g / m². 2 ~80g / m 2 or 5 g / m 2 ~50g / m 2 of porous substrate, or 10 g / m 2 ~30g / m 2 As should be understood, multiple passes of ionomer coating result in one or more layers of the treated porous substrate having a continuous ionomer phase with no internal interfaces within the layer of ionomer or between multiple coatings of ionomer.

[0084] In an alternative embodiment, another untreated porous substrate can be contacted with the coated and treated porous substrate, impregnating the untreated porous substrate with the impregnating solution to create a treated porous substrate having multiple layers (i.e., a multi-pass ionomer composite membrane). This process can be repeated any number of times (e.g., twice) without a drying step between each pass of coating to create a treated porous substrate having multiple layers. The resulting multi-pass composite membrane has a thickness in the range of 10-150 microns at 0% RH, 15-80 microns at 0% RH, or 20-60 microns at 0% RH, and optionally has a thickness of 3 g / m 2 ~80g / m 2 or 5 g / m 2 ~50g / m 2 or 10 g / m 2 ~30g / m 2 As should be understood, multiple passes of ionomer coating result in a composite membrane having one or more layers of treated porous substrate with a continuous ionomer phase with no internal interfaces within the layer of ionomer or between multiple coatings of ionomer.

[0085] The treated porous substrate can be placed in an oven to dry and thermally anneal. The oven temperature can range from 60° C. to 220° C., but is preferably from 150° C. to 200° C. Upon drying and thermally annealing the treated porous substrate in the oven, the ion exchange material becomes firmly attached to the internal membrane surface and, optionally, to the external membrane surface, e.g., the fibrils and / or nodes of the porous substrate.

[0086] In embodiments in which a surfactant is used, the treated porous substrate is further treated to remove the surfactant. This is accomplished by immersing or submerging the treated porous substrate in a solution of, for example, water, isopropyl alcohol, hydrogen peroxide, methanol, and / or glycerin. During this process, the surfactant that was originally mixed with the ion exchange material in the solution is removed. This immersion or submersion causes slight swelling of the treated porous substrate, but the ion exchange material remains within the interior volume of the porous substrate.

[0087] The treated porous substrate is treated by boiling in a suitable swelling agent, preferably water, to slightly swell the membrane in the x, y, and z directions. The swollen treated porous substrate has a higher and stronger ion transport rate. Unlike membranes made solely of ion exchange material, the swollen treated porous substrate retains its mechanical integrity and dimensional stability while maintaining desirable ion transport properties. There is a correlation between the swelling agent content in the treated porous substrate and the transport properties of the treated porous substrate. The swollen treated porous substrate transports chemical species faster than the unswollen treated porous substrate.

[0088] d. Properties of the composite membrane Composite membranes having a continuous ionomer phase according to embodiments of the present invention have a predetermined transparency. Haze refers to the optical clarity with which objects can be seen when viewed through the composite membrane and can be measured with a haze meter or transparency meter. In some embodiments, composite membranes having a continuous ionomer phase formed by a single pass of ionomer coating have a haze of 5% to 95%, or 10% to 90%, or 20% to 85%. In alternative embodiments, composite membranes having a continuous ionomer phase formed through multiple passes of ionomer coating without a drying step between each pass of coating have a haze of 5% to 95%, or 10% to 90%, or 20% to 85%.

[0089] III. Flow Battery As described above, composite membranes fabricated according to embodiments of the present invention (see, e.g., FIGS. 3A-3F) can be incorporated into flow batteries (e.g., redox flow batteries). As shown in FIG. 4, a flow battery 400 is provided according to an embodiment of the present invention. The flow battery 400 is a fully rechargeable electrical energy storage device that includes a reservoir 410 containing a catholyte or positive electrolyte fluid 420 and a second reservoir 430 containing an anolyte or negative electrolyte fluid 440. The catholyte 420 can be an electrolyte containing specific redox ions that are either in an oxidized state and are reduced during the discharge process of the flow battery 400, or in a reduced state and are oxidized during the charge process of the flow battery 400, or a mixture of these oxidized ions and ions to be oxidized. Anolyte 440 can be an electrolyte containing redox ions that are in a reduced state and are oxidized during the discharge process of flow battery 400, or that are in an oxidized state and are reduced during the charge process of flow battery 900, or that are a mixture of reduced ions and ions that must be reduced.

[0090] Catholyte 420 is circulated by pump 450 through exchange region 460, which includes a composite membrane 465 disposed between a cathode 470 and an anode 480. Anolyte 440 is also circulated by pump 490 through exchange region 460. Composite membrane 465 is fabricated according to an embodiment of the present invention (see, e.g., Figures 3A-3D).

[0091] In some embodiments, the amount of catholyte 420 and anolyte 440 provided to exchange region 460 can be varied by the pumping action of pumps 450 and 490, thus varying the amount of power generated by the electrolyte reaction in exchange region 460. Both catholyte 420 and anolyte 440 circulate within their own respective spaces, promoting reduction / oxidation chemical processes on either side of composite membrane 465 and resulting in an electrical potential. The cell voltage can be determined chemically by the Nernst equation and ranges from 0.5 to 5.0 volts or 0.8 to 1.7 volts.

[0092] IV. Test Procedures A. Testing of Ion Exchange Materials (a) Solids concentration of the solution of ion exchange material (IEM) The terms "solution" and "dispersion" are used interchangeably herein when referring to IEM. This test procedure is appropriate for solutions in which the IEM is in protonated form and negligible amounts of other solids are present. A 2 cubic centimeter volume of IEM solution was drawn into a syringe, and the mass of the syringe containing the solution was measured using a balance in a solids analyzer (obtained from CEM Corporation, USA). The mass of two sheets of glass fiber paper (obtained from CEM Corporation, USA) was also measured and recorded. The IEM solution was then deposited from the syringe onto two layers of glass fiber paper. The glass fiber paper containing the ion exchange material was placed in the solids analyzer and heated to 160°C to remove the solvent liquid. The mass of the glass fiber paper and residual solids was recorded when it no longer changed with increasing temperature and time. The residual IEM was assumed to contain no water (i.e., the mass of the ionomer corresponding to 0% RH). The mass of the empty syringe was then measured using the same balance as before and recorded. The ionomer solids content in the solution was calculated according to the following formula:

number

[0093] (b) Equivalent weight of ion exchange material (IEM) The following test procedure is appropriate for IEMs containing a single ionomer resin or a mixture of ionomer resins that are in the protonated form (i.e., contain negligible amounts of other cations) and in a solution containing negligible amounts of other ionic species, including protonic acids and dissociable salts. If these conditions are not met, the solution must be purified from ionic impurities prior to testing according to appropriate procedures known to those skilled in the art, or the impurities must be characterized and their effect on the EW test results corrected for.

[0094] As used herein, the EW of an IEM refers to the IEM in its proton form at 0% RH and containing negligible impurities. The IEM can contain a single ionomer or a mixture of ionomers in proton form. An amount of IEM solution containing 0.2 grams of solids and having the solids concentration determined above was poured into a plastic cup. The mass of the ion exchange material was measured using a conventional laboratory scale (obtained from Mettler Toledo, LLC, USA). Five milliliters of deionized water and five milliliters of 200-proof denatured ethanol (SDA 3C, Sigma Aldrich, USA) were then added to the ion exchange material in the cup. Next, 55 ml of 2N aqueous sodium chloride solution was added to the IEM solution. The sample was then allowed to equilibrate for 15 minutes with constant stirring. After the equilibration step, the sample was titrated with 1N sodium hydroxide solution. The volume of 1N sodium hydroxide solution required to neutralize the sample solution to a pH value of 7 was recorded. The EW of the IEM (EW) was calculated. IEM ) was calculated as follows:

number

[0095] When multiple IEMs were combined to form a composite membrane, the average EW of the IEMs in the composite membrane was calculated using the following formula:

number

[0096] B. Porous Membrane Testing (a) Bubble point of porous membrane Bubble point was measured according to the procedure of ASTM F316-86 (1986). Isopropyl alcohol was used as the wetting fluid to fill the pores of the specimen. The bubble point is the air pressure required to create an initial continuous flow of air bubbles, detectable by the rise of the bubbles through a layer of isopropyl alcohol covering a microporous polymer matrix. This measurement provides an estimate of the maximum pore size.

[0097] (b) Gurley number of porous membrane Gas flow barrier properties were measured using a Gurley density meter according to ASTM D-726-58 (1971). The procedure involves clamping the sample between the permeable plates of the Gurley density meter. A freely sliding inner tube of known weight is then released. The Gurley number is defined as the time in seconds it takes for the released inner tube to displace a specific amount of air in the density meter through the sample material.

[0098] (c) Non-contact thickness of porous membrane A sample of the microporous polymer structure was placed on a flat, smooth metal anvil and tensioned to remove wrinkles. The height of the microporous polymer structure above the anvil was measured and recorded using a non-contact Keyence LS-7010M digital micrometer. The height of the anvil without the microporous polymer matrix was then recorded. The thickness of the microporous polymer structure was taken as the difference between the micrometer readings with and without the microporous structure present on the anvil.

[0099] (d) Mass per area of ​​porous membrane Each microporous polymer structure was distorted sufficiently to remove wrinkles and then cut into 10 cm pieces using a die. 2 A piece of 10cm was cut out. 2 The pieces were weighed on a conventional laboratory scale. The mass per area (M / A) was then calculated as the ratio of the measured mass to the known area. This procedure was repeated twice, and the average M / A was calculated.

[0100] (e) Apparent density of porous membrane The apparent density of the microporous polymer structure was calculated using the non-contact thickness and mass per area data using the following formula:

number

[0101] C. Testing of Composite Membranes (a) Thickness of the composite membrane The composite films were equilibrated in the thickness measurement chamber for at least 1 hour before measurement. The composite films were left attached to the substrates on which they were coated. For each sample, the composite film on the coated substrate was placed on a smooth, flat, and level marble slab. A thickness gauge (obtained from Heidenhain Corporation, USA) was contacted with the composite film, and height readings on the gauge were recorded at six different spots arranged in a grid pattern on the film. The sample was then removed from the substrate, the gauge was contacted with the substrate, and height readings were again recorded at the same six spots. The average thickness of the composite film at a given relative humidity (RH) in the chamber was calculated as the difference between the height readings on the gauge with and without the composite film on the coated substrate. The local RH of the room was measured using an RH probe (obtained from Fluke Corporation). The thickness at 0% RH was calculated using the following general formula:

number

number

[0102] (b) Mass per area of ​​the composite membrane The following test procedure can be used to determine the mass per area of ​​a composite membrane prepared according to embodiments of the present disclosure: 2 A sample of the composite material, including the substrate and composite membrane, was cut from the sheet. After cutting, the sample of the composite membrane on the coated substrate was weighed on a conventional laboratory scale, and its mass was recorded along with the value of RH surrounding the laboratory scale at the time of measurement. The local RH in the chamber was measured using an RH probe (obtained from Fluke Corporation). The sample was then removed from the substrate, and the substrate was weighed using the same laboratory scale, and the substrate weight was recorded. The mass of the composite membrane at a given RH in the chamber was calculated as the difference between the mass readings on the scale with and without the composite membrane on the coated substrate.

[0103] The mass per area of ​​the composite membrane at 0% RH is then calculated according to the following formula:

number

[0104] (c) Haze of the composite film The following haze test procedure was used on a sample of an ion exchange membrane having a continuous ionomer phase prepared according to an embodiment of the present invention (see, e.g., Figures 3A-3F). The haze test is performed on a composite membrane that has been dried at ambient conditions (e.g., 20-22°C, 30-70% relative humidity) for at least 24 hours before testing. As shown in Figures 5A and 5B, the haze test procedure involves using a hazemeter or transparency meter 500 to determine the wide-angle scattering of light by the ion exchange membrane, which results in a loss of optical contrast that allows objects to be seen when viewed through the ion exchange membrane. In hazemeter or transparency meter 500 implemented according to an embodiment of the present invention, sample 505 (e.g., an ion exchange membrane having a continuous ionomer phase) is positioned between light source 510 and light integrating sphere 515. The light integrating sphere is lined with a diffusely reflective material and equipped with a photodetector 520, a movable diffusely reflective surface 525, and traps 530 for low-angle scattered and directly transmitted light.

[0105] First, the total transmittance of the sample 505 is measured with the low-angle scattered and direct transmission light trap 530 closed by a diffuse reflecting surface, as shown in FIG. 5A. With the low-angle scattered and direct transmission light trap 530 closed, all light passing through the sample 505 is detected. Total light transmittance is defined as the ratio of light transmitted by the sample to the light incident on the sample. Then, the haze of the sample 505 is measured with the low-angle scattered and direct transmission light trap 530 open, as shown in FIG. 5B. With the low-angle scattered and direct transmission light trap 530 open, only the diffuse component of the light passing through the sample 505 is detected. Haze is defined as the ratio of diffuse transmittance to the total transmittance of light passing through the sample.

[0106] In some embodiments, the haze of a composite membrane having a continuous ionomer phase formed by a single pass of ionomer coating is 5% to 95%, or 10% to 90%, or 20% to 85%. In alternative embodiments, the haze of a continuous ionomer phase formed through multiple passes of ionomer coating without a drying step between each pass of coating is 5% to 95%, or 10% to 90%, or 20% to 85%.

[0107] (d) Blistering of composite membrane The following blister test procedure was used on composite membrane samples prepared according to embodiments of the present invention (see, e.g., Figures 3A-3D). The blister test procedure involved subjecting each composite membrane sample to a stress cycle in which it was immersed in a beaker containing a 6 mol / L aqueous sulfuric acid solution at 80°C for 3 minutes, followed by a 1-minute immersion in a beaker containing deionized water at ambient conditions (e.g., 20-22°C, 30-70% relative humidity). The stress cycle was repeated six times consecutively. After the stress cycle, each composite membrane sample was dried at ambient conditions (e.g., 20-22°C, 30-70% relative humidity), and the bubble or blister density was counted. The bubble or blister area can be calculated in a number of ways, including manual observation and measurement and / or automated techniques such as the use of imaging software. An example of publicly available image processing software that can be used to calculate the number and area of ​​blisters is ImageJ, developed at the National Institutes of Health.

[0108] 6A to 6B are 3×3 cm samples before the blister test. 2 Low resolution and 1×1cm 2 High resolution and 1x1cm after blister test 26A-6D show high resolution images of a composite membrane 600 prepared in accordance with an embodiment of the present invention (see, e.g., FIGS. 3A-3D) and a conventional ion exchange membrane 602. As shown in FIG. 6A, both the composite membrane 600 and the conventional ion exchange membrane 602 exhibit no blisters prior to blister testing performed according to the blister testing procedure provided above. As shown in FIG. 6B, the composite membrane 600 exhibits no blisters (i.e., 0 blisters / cm). 2 ), thus the membrane has 0% blister area, whereas the conventional ion exchange membrane 602 exhibits blisters (i.e., 95 blisters / cm 2 , each blister has a radius of 200 μm, and the membrane has a blister area of ​​13.5%).

[0109] In some embodiments, composite membranes having a continuous ionomer phase formed via a single pass of ionomer coating and subjected to a blister test procedure have a bubble or blister area of ​​less than 0.3%, less than 0.2%, less than 0.1%, or 0%. In alternative embodiments, composite membranes having a continuous ionomer phase formed via multiple passes of ionomer coating without a drying step between each pass of coating and subjected to a blister test procedure have a bubble or blister area of ​​less than 0.3%, less than 0.2%, less than 0.1%, or 0%. Figures 7A-7C show composite membrane samples 700, 710, and 720 prepared according to embodiments of the present invention and having a bubble or blister density of less than 0.1%. In some embodiments, composite membranes having a continuous ionomer phase formed via a single pass of ionomer coating and subjected to a blister test procedure have a change in haze of 0% or less, 0% to -60%, 0% to -45%, 0% to -30%, or 0% to -21%. In alternative embodiments, a composite membrane having a continuous ionomer phase formed through multiple passes of ionomer coating without a drying step between each pass of coating and subjected to a blister test has a change in haze of 0% or less, 0% to -60%, or 0% to -45%, or 0% to -30%, or 0% to -21%. [Example]

[0110] V. Example Without intending to limit the scope of the invention, the device and manufacturing method of the present invention may be better understood by reference to the following examples. All samples of ePTFE provided in the following examples were made in accordance with the teachings of U.S. Patent No. 3,593,566. A summary of the physical properties of the porous expanded polytetrafluoroethylene (ePTFE) is shown in Table 1. [Table 1]

[0111] 1. Comparative Example - Conventional Multiple-Pass Ionomer Produced with Drying Between Each Step Example 1.1 A 26.7-micron-thick composite membrane containing an ion-exchange polymer, perfluorosulfonic acid resin, with an EW of 920 g / mol acid equivalent (EW) was prepared using conventional laboratory techniques. First, a water-ethanol solution of perfluorosulfonic acid resin (product FSS2, available from Asahi Glass Co., Ltd.) with an EW of 920 g / mol equivalent was coated onto a moving carrier substrate using a slot die and laminated with the ePTFE membrane #5, which was moving in the same direction. The carrier substrate was a polymer sheet (available from DAICEL VALUE COATING LTD., Japan) containing PET and a protective layer of cyclic olefin copolymer (COC), oriented with the COC side facing up. The laminate was then dried in an oven at 160 °C and annealed at that temperature for 1 minute to produce a solid-coated structure containing the carrier substrate bonded to the polymer layer reinforced with expanded porous polytetrafluoroethylene.

[0112] Subsequently, another amount of the same water-ethanol solution of perfluorosulfonic acid resin was applied to the coated structure using a slot die and laminated with another ePTFE membrane #5 moving in the same direction. The laminate was again dried at 160°C and annealed at that temperature for 1 minute. Finally, another amount of the same water-ethanol solution of perfluorosulfonic acid resin was applied to the coated structure using a slot die and again dried at 160°C and annealed at that temperature for 1 minute. The resulting composite membrane included a carrier substrate bonded to an ion-exchange polymer layer, followed by a microporous polytetrafluoroethylene membrane layer with an ion-exchange polymer embedded therein, followed by another microporous polytetrafluoroethylene membrane layer with another ion-exchange polymer embedded therein, followed by another ion-exchange polymer on top, with a total thickness of 26.7 microns at 0% RH and a mass / area of ​​54.0 g / m 2 The composite film was almost transparent, with a haze value of 5%.

[0113] To determine properties such as the susceptibility of the composite membrane to blister formation in a total liquid environment with varying ionic strength, the blister test procedure was performed as described above. The haze of Sample 1.5, a composite membrane with a discontinuous ionomer phase, after the blister test as described above increased by 320% to a value of 21.0%. The bubble or blister area of ​​the composite membrane sample with a discontinuous ionomer phase prepared as described above was measured as a ratio of the area of ​​the ionomer to the area of ​​the bubbles or blisters in the ionomer, to approximately 13.5%. Figure 6B shows photographs of 3 cm × 3 cm and 1 cm × 1 cm plan views of the composite membrane 602 representing Example 1.1 before and after the blister test was performed. The membrane after the blister test had bubbles or blisters 604 at weak internal interfaces within the ionomer layer or between multiple coatings of ionomer.

[0114] Example 1.2 A 44.2-micron-thick composite membrane containing an ion-exchange polymer perfluorosulfonic acid resin with an EW of 810 g / mol acid equivalent (EW) reinforced with one layer of expanded porous ePTFE membrane #2 was prepared using conventional laboratory techniques. First, a water-ethanol solution of ion-exchange perfluorosulfonic acid resin with an EW of 810 g / mol equivalent (obtained from Shanghai Gore 3F Fluoromaterials Co., Ltd., China) was coated onto a carrier substrate restrained in a frame using a drawdown bar and laminated with ePTFE membrane #2. The carrier substrate was a polymer sheet (obtained from DAICEL VALUE COATING LTD., Japan) containing a protective layer of PET and cyclic olefin copolymer (COC), oriented with the COC side facing up. The laminate was then dried in an oven at 160°C and annealed at that temperature for 1 minute. Another amount of the same water-ethanol solution of perfluorosulfonic acid resin was then applied to the coated structure using a drawdown bar, dried again at 160°C, and annealed at that temperature for 1 minute. The resulting composite membrane, comprising a carrier substrate bonded to an ion-exchange polymer layer, followed by a microporous polytetrafluoroethylene membrane layer on top of which the ion-exchange polymer was embedded with another ion-exchange polymer layer, had a total thickness of 44.2 microns at 0% RH and a mass / area of ​​90.5 g / m. 2 The composite film was almost transparent, with a haze value of 4.6%.

[0115] To determine properties such as the susceptibility of the composite membrane to blister formation in a total liquid environment with varying ionic strength, the blister test procedure was performed as described above, and the membrane after the blister test had bubbles or blisters within the ionomer layer and at weak internal interfaces between multiple coatings of ionomer, as described above. After the blister test procedure as described above, the haze of Sample 1.2, a composite membrane with a discontinuous ionomer phase, increased by 35% to a value of 6.3%. The bubble or blister area of ​​Sample 1.2, a composite membrane with a discontinuous ionomer phase prepared as described above, was measured as a ratio of the area of ​​the ionomer to the area of ​​the bubbles or blisters in the ionomer, to be approximately 1.3%.

[0116] Example 1.3 A 27.9-micron-thick composite membrane containing a perfluorosulfonic acid resin ion exchange polymer with an EW of 1100 g / mol acid equivalent (EW) reinforced with one layer of expanded porous ePTFE membrane #2 was prepared using conventional laboratory techniques. First, a water-ethanol solution of perfluorosulfonic acid resin with an EW of 1100 g / mol equivalent (D2021, obtained from Ion Power Inc., USA) was coated onto a carrier substrate restrained by a frame using a drawdown bar, and then laminated with ePTFE membrane #2. The carrier substrate was a polymer sheet (obtained from DAICEL VALUE COATING LTD., Japan) containing PET and a protective layer of cyclic olefin copolymer (COC), oriented with the COC side facing up. The laminate was then dried in an oven at 160 °C and annealed at that temperature for 1 minute. Another amount of the same water-ethanol solution of perfluorosulfonic acid resin was then applied to the coated structure using a drawdown bar, dried again at 160°C, and annealed at that temperature for 1 minute. The resulting composite membrane, comprising a carrier substrate bonded to an ion-exchange polymer layer, followed by a microporous polytetrafluoroethylene membrane layer on top of which the ion-exchange polymer was embedded with another ion-exchange polymer layer, had a total thickness of 27.9 microns and a mass / area of ​​58.4 g / m at 0% RH. 2The composite film was almost transparent, with a haze value of 16.8%.

[0117] To determine properties such as the susceptibility of the composite membrane to blister formation in a total liquid environment with varying ionic strength, the blister test procedure was performed as described above, and the membrane after the blister test had bubbles or blisters within the ionomer layer and at weak internal interfaces between multiple coatings of ionomer. The haze of Sample 1.3, a composite membrane with a discontinuous ionomer phase, after the blister test as described above increased by 34% to a value of 22.6%. The bubble or blister area of ​​Sample 1.3, a composite membrane with a discontinuous ionomer phase prepared as described above, was approximately 0.5%, measured as the ratio of the area of ​​the ionomer to the area of ​​the bubbles or blisters in the ionomer.

[0118] Example 1.4 A 22.7-micron-thick composite membrane containing a perfluorosulfonic acid resin ion-exchange polymer with an EW of 900 g / mol acid equivalent (EW) reinforced with one layer of expanded porous ePTFE membrane #3 was prepared using conventional laboratory techniques. First, a water-ethanol solution of perfluorosulfonic acid resin with an EW of 900 g / mol equivalent (obtained from Shanghai Gore 3F Fluoromaterials Co., Ltd., China) was coated onto a carrier substrate restrained by a frame using a drawdown bar, and then laminated with ePTFE membrane #3. The carrier substrate was a polymer sheet (obtained from DAICEL VALUE COATING LTD., Japan) containing PET and a protective layer of cyclic olefin copolymer (COC), oriented with the COC side facing up. The laminate was then dried in an oven at 160°C and annealed at that temperature for 1 minute. Another amount of the same water-ethanol solution of perfluorosulfonic acid resin was then applied to the coated structure using a drawdown bar, dried again at 160°C, and annealed at that temperature for 1 minute. The resulting composite membrane, comprising a carrier substrate bonded to an ion-exchange polymer layer, followed by a microporous polytetrafluoroethylene membrane layer on top of which the ion-exchange polymer was embedded with another ion-exchange polymer layer, had a total thickness of 22.7 microns and a mass / area of ​​47.1 g / m at 0% RH. 2 The composite film was almost transparent, with a haze value of 19.4%.

[0119] To determine properties such as the susceptibility of the composite membrane to blister formation in a total liquid environment with varying ionic strength, the blister test procedure was performed as described above, and the membrane after the blister test had bubbles or blisters within the ionomer layer and at weak internal interfaces between multiple coatings of ionomer. The haze of Sample 1.4, a composite membrane with a discontinuous ionomer phase, after the blister test described above increased by 45% to a value of 28%. The bubble or blister area of ​​Sample 1.4, a composite membrane with a discontinuous ionomer phase prepared as described above, was approximately 0.3%, measured as the ratio of the area of ​​the ionomer to the area of ​​the bubbles or blisters in the ionomer.

[0120] Example 1.5 A 17.9-micron-thick composite membrane containing a perfluorosulfonic acid resin ion exchange polymer with an EW of 900 g / mol acid equivalent (EW) reinforced with one layer of expanded porous ePTFE membrane #4 was prepared using conventional laboratory techniques. First, a water-ethanol solution of perfluorosulfonic acid resin with an EW of 900 g / mol equivalent (obtained from Shanghai Gore 3F Fluoromaterials Co., Ltd., China) was coated onto a frame-restrained carrier substrate using a drawdown bar and laminated with ePTFE membrane #4. The carrier substrate was a polymer sheet (obtained from DAICEL VALUE COATING LTD., Japan) containing PET and a protective layer of cyclic olefin copolymer (COC), oriented with the COC side facing up. The laminate was then dried in an oven at 160 °C and annealed at that temperature for 1 minute. Another amount of the same water-ethanol solution of perfluorosulfonic acid resin was then applied to the coated structure using a drawdown bar, dried again at 160°C, and annealed at that temperature for 1 minute. The resulting composite membrane, comprising a carrier substrate bonded to an ion-exchange polymer layer, followed by a microporous polytetrafluoroethylene membrane layer on top of which the ion-exchange polymer was embedded with another ion-exchange polymer layer, had a total thickness of 17.9 microns and a mass / area of ​​36.7 g / m at 0% RH. 2 The composite film was almost transparent, with a haze value of 5.7%.

[0121] To determine properties such as the susceptibility of the composite membrane to blister formation in a total liquid environment with varying ionic strength, the blister test procedure was performed as described above, and the membrane after the blister test had bubbles or blisters at weak internal interfaces between layers of ionomer or multiple coatings of ionomer. The haze of Sample 1.5, a composite membrane with a discontinuous ionomer phase, after the blister test as described above increased by 31% to a value of 7.5%. The bubble or blister area of ​​the sample composite membrane 1.5 with a discontinuous ionomer phase prepared as described above was approximately 6.3%, measured as the ratio of the area of ​​the ionomer to the area of ​​the bubbles or blisters in the ionomer. The data for Comparative Examples 1.1 to 1.5 are summarized in Table 2. [Table 2]

[0122] 2. Inventive Example - Composite Membrane with a Continuous Ionomer Phase Produced by Single-Pass Ionomer Coating According to an Embodiment of the Invention Example 2.1 A 21.6-micron-thick composite membrane containing an ion-exchange polymer, perfluorosulfonic acid resin, with an EW of 820 g / mol acid equivalent (EW) was prepared using conventional laboratory techniques. First, a water-ethanol solution of perfluorosulfonic acid resin (product IW100-800 obtained from Asahi Glass Co., Ltd.) with an EW of 820 g / mol acid equivalent was coated onto a moving carrier substrate using a slot die, and then laminated with ePTFE membrane #3, which was moving in the same direction. The carrier substrate was a polymer sheet (obtained from DAICEL VALUE COATING LTD., Japan) containing PET and a protective layer of cyclic olefin copolymer (COC), oriented with the COC side facing up. The laminate was then dried in an oven at 160°C and annealed at that temperature for 1 minute to produce a solid coated structure comprising a carrier substrate bonded to an ion exchange polymer layer, followed by a microporous polytetrafluoroethylene membrane layer with an ion exchange polymer embedded therein, with a total thickness of 21.6 microns and a mass / area of ​​44.9 g / m at 0% RH. 2 As can be seen in Figures 3E-3F, the resulting composite membrane was characterized by having the ion exchange material embedded within the microporous polymer structure, leaving an unoccluded portion of the microporous polymer structure closest to the first surface and forming a layer on the second surface of the microporous polymer structure. The resulting composite membrane had a haze value of 65%.

[0123] To determine properties such as the susceptibility of the composite membrane to blister formation in a total liquid environment with varying ionic strength, the blister test procedure was performed as described above. The haze of Sample 2.1, a composite membrane containing a discontinuous ionomer phase, after the blister test as described above decreased by -6.2% to a value of 61.0%. The bubble or blister area of ​​Sample 2.1, a composite membrane with a continuous ionomer phase prepared as described above, was approximately 0%, measured as the ratio of the ionomer area to the bubble or blister area in the ionomer. Figure 6A shows photographs of 3 cm x 3 cm and 1 cm x 1 cm cross-sectional views of composite membrane 600 before and after the blister test was performed; the membrane after the blister test was free of bubbles or blisters.

[0124] Example 2.2 A 44.6-micron-thick composite membrane containing a perfluorosulfonic acid resin ion-exchange polymer with an EW of 810 g / mol acid equivalent (EW) and reinforced with one layer of expanded porous ePTFE membrane #1 was prepared using conventional laboratory techniques. First, a water-ethanol solution of perfluorosulfonic acid resin with an EW of 810 g / mol equivalent (obtained from Shanghai Gore 3F Fluoromaterials Co., Ltd., China) was coated onto a carrier substrate restrained by a frame using a drawdown bar and laminated with ePTFE membrane #1. The carrier substrate was a polymer sheet (obtained from DAICEL VALUE COATING LTD., Japan) containing PET and a protective layer of cyclic olefin copolymer (COC), oriented with the COC side facing up. The laminate was then dried in an oven at 160 °C and annealed at that temperature for 1 minute to produce a solid-coated structure containing the carrier substrate bonded to the polymer layer reinforced with expanded porous polytetrafluoroethylene. The resulting composite membrane, comprising a carrier substrate bonded to an ion exchange polymer layer, followed by a microporous polytetrafluoroethylene membrane layer with an ion exchange polymer embedded therein, had a total thickness of 44.6 microns and a mass / area of ​​91.8 g / m at 0% RH. 2The resulting composite membrane was characterized by having an ion exchange material embedded within a microporous polymer structure, leaving an unoccluded portion of the microporous polymer structure nearest the first surface and forming a layer on the second surface of the microporous polymer structure. The haze value of the composite membrane was 24.4%.

[0125] To determine properties such as the susceptibility of the composite membrane to blister formation in all-liquid environments with varying ionic strength, the blister test procedure was performed as described above, and the composite membrane was free of bubbles or blisters after the blister test. The haze of Sample 2.2, a composite membrane with a continuous ionomer phase, after the blister test as described above decreased by -11.3% to a value of 21.6%. The bubble or blister area of ​​Sample 2.2, a composite membrane with a continuous ionomer phase prepared as described above, was approximately 0%, measured as the ratio of the area of ​​the ionomer to the area of ​​the bubbles or blisters in the ionomer.

[0126] Example 2.3 A 28.1-micron-thick composite membrane containing an ion-exchange polymer, perfluorosulfonic acid resin, with an EW of 1100 g / mol acid equivalent (EW) was prepared using conventional laboratory techniques. First, a water-ethanol solution of perfluorosulfonic acid resin (D2021, obtained from Ion Power Inc., USA) with an EW of 1100 g / mol equivalent was coated onto a carrier substrate restrained by a frame using a drawdown bar, and then laminated with ePTFE membrane #1. The carrier substrate was a polymer sheet (obtained from DAICEL VALUE COATING LTD., Japan) containing PET and a protective layer of cyclic olefin copolymer (COC), oriented with the COC side facing up. The laminate was then dried in an oven at 160 °C and annealed at that temperature for 1 minute. The resulting composite membrane comprised a carrier substrate bonded to a microporous polytetrafluoroethylene membrane layer with an ion exchange polymer embedded therein, and had a total thickness of 28.1 microns and a mass of 59.5 g / m at 0% RH. 2The resulting composite membrane was characterized by having an ion exchange material embedded within the microporous polymer structure, leaving an unblocked portion of the microporous polymer structure closest to the first surface, and no layer on the second surface of the microporous polymer structure. The haze value of the composite membrane was 27.8%.

[0127] To determine properties such as the susceptibility of the composite membrane to blister formation in a total liquid environment with varying ionic strength, the blister test procedure was performed as described above, and the composite membrane after the blister test was free of bubbles or blisters. The haze of Sample 2.3, a composite membrane with a continuous ionomer phase, after the blister test as described above decreased by -5.9% to a value of 26.2%. The bubble or blister area of ​​Sample 2.3, a composite membrane with a continuous ionomer phase prepared as described above, was approximately 0%, measured as the ratio of the area of ​​the ionomer to the area of ​​the bubbles or blisters in the ionomer.

[0128] Example 2.4 A 23.2-micron-thick composite membrane containing a perfluorosulfonic acid resin ion-exchange polymer with an EW of 900 g / mol acid equivalent (EW) reinforced with one layer of expanded porous ePTFE membrane #2 was prepared using conventional laboratory techniques. First, a water-ethanol solution of perfluorosulfonic acid resin with an EW of 900 g / mol equivalent (obtained from Shanghai Gore 3F Fluoromaterials Co., Ltd., China) was coated onto a carrier substrate restrained by a frame using a drawdown bar, and then laminated with ePTFE membrane #2. The carrier substrate was a polymer sheet (obtained from DAICEL VALUE COATING LTD., Japan) containing PET and a protective layer of cyclic olefin copolymer (COC), oriented with the COC side facing up. The laminate was then dried in an oven at 160 °C and annealed at that temperature for 1 minute. The resulting composite membrane, comprising a carrier substrate bonded to a microporous polytetrafluoroethylene membrane layer with an embedded ion exchange polymer, had a total thickness of 23.2 microns and a mass / area of ​​49.2 g / m at 0% RH. 2The resulting composite membrane was characterized by having an ion exchange material embedded within the microporous polymer structure, leaving an unblocked portion of the microporous polymer structure closest to the first surface, and no layer on the second surface of the microporous polymer structure. The haze value of the composite membrane was 35.2%.

[0129] To determine properties such as the susceptibility of the composite membrane to blister formation in all-liquid environments with varying ionic strength, the blister test procedure was performed as described above, and the composite membrane after the blister test was free of bubbles or blisters. The haze of Sample 2.4, a composite membrane with a continuous ionomer phase, after the blister test as described above decreased by -20.7% to a value of 27.9%. The bubble or blister area of ​​Sample 2.4, a composite membrane with a continuous ionomer phase prepared as described above, was approximately 0%, measured as the ratio of the area of ​​the ionomer to the area of ​​the bubbles or blisters in the ionomer.

[0130] Example 2.5 An 18.4-micron-thick composite membrane containing an ion-exchange polymer, perfluorosulfonic acid resin, with an EW of 900 g / mol acid equivalent (EW) and reinforced with one layer of expanded porous ePTFE membrane #3 was prepared using conventional laboratory techniques. First, a water-ethanol solution of perfluorosulfonic acid resin with an EW of 900 g / mol equivalent (obtained from Shanghai Gore 3F Fluoromaterials Co., Ltd., China) was coated onto a carrier substrate restrained by a frame using a drawdown bar, and then laminated with ePTFE membrane #3. The carrier substrate was a polymer sheet (obtained from DAICEL VALUE COATING LTD., Japan) containing PET and a protective layer of cyclic olefin copolymer (COC), oriented with the COC side facing up. The laminate was then dried in an oven at 160 °C and annealed at that temperature for 1 minute. The resulting composite membrane, comprising a carrier substrate bonded to a polymer layer reinforced with expanded porous polytetrafluoroethylene, had a total thickness of 18.4 microns and a mass / area of ​​38.6 g / m at 0% RH. 2The resulting composite membrane was characterized by having an ion exchange material embedded within a microporous polymer structure, leaving an unoccluded portion of the microporous polymer structure nearest the first surface, and having a layer on the second surface of the microporous polymer structure. The haze value of the composite membrane was 77.3%.

[0131] To determine properties such as the susceptibility of the composite membrane to blister formation in a total liquid environment with varying ionic strength, the blister test procedure was performed as described above, and the composite membrane after the blister test was free of bubbles or blisters. The haze of Sample 2.5, a composite membrane with a continuous ionomer phase, after the blister test as described above decreased by -8.7% to a value of 60.5%. The bubble or blister area of ​​Sample 2.5, a composite membrane with a continuous ionomer phase prepared as described above, was approximately 0%, measured as the ratio of the area of ​​the ionomer to the area of ​​the bubbles or blisters in the ionomer.

[0132] The data for Inventive Examples 2.1 to 2.5 are summarized in Table 3. [Table 3]

[0133] Although the present invention has been described in detail, modifications within the spirit and scope of the present invention will be readily apparent to those skilled in the art. It should be understood that aspects of the present invention and parts of the various embodiments, as well as various features recited above and / or in the appended claims, may be combined or interchanged in whole or in part. In the above description of various embodiments, those embodiments that refer to other embodiments may be appropriately combined with other embodiments, as will be understood by those skilled in the art. Furthermore, those skilled in the art will appreciate that the above description is merely exemplary and is not intended to limit the present invention. Aspects of the present invention are listed below. [Aspect 1] a microporous polymer structure, and an ion exchange material at least partially embedded within said microporous polymer structure, rendering at least a portion of said microporous polymer structure occlusive; wherein the ion exchange material forms a continuous ionomer phase within the composite membrane, and wherein the composite membrane exhibits a haze change of 0% or less after being subjected to a blister test procedure. [Aspect 2] 2. The composite membrane of embodiment 1, further comprising an additional layer of ion exchange material provided on a bottom surface of the composite membrane. [Aspect 3] 3. The composite membrane of any one of the preceding claims, wherein the microporous polymer structure comprises at least two microporous polymer layers. [Aspect 4] The blister test procedure includes: In step 1, the composite membrane is immersed in a 6 mol / L aqueous sulfuric acid solution at 80°C for 3 minutes; In step 2, removing the composite membrane from the sulfuric acid aqueous solution; Step 3: immersing the composite membrane in deionized water at ambient conditions for 1 minute; In step 4, removing the composite membrane from the deionized water and repeating the cycle consisting of steps 1 to 4 at least twice; Step 5: drying the composite membrane at ambient conditions; and In step 6, counting bubbles or blisters formed on the composite film; 4. The composite membrane of any one of embodiments 1 to 3, comprising: [Aspect 5] 5. The composite membrane of embodiment 4, wherein the composite membrane having a continuous ionomer phase has a bubble or blister area of ​​less than 0.3% after being subjected to said blister testing procedure. [Aspect 6] 5. The composite membrane of embodiment 4, wherein the composite membrane having a continuous ionomer phase has 0% bubble or blister area after being subjected to said blister testing procedure. [Aspect 7] 5. The composite film of embodiment 4, wherein the composite film exhibits a haze change of 0% to −60% after being subjected to the blister test procedure. [Aspect 8] 5. The composite film of embodiment 4, wherein the composite film exhibits a haze change of 0% to −45% after being subjected to the blister test procedure. [Aspect 9] 5. The composite film of embodiment 4, wherein the composite film exhibits a haze change of 0% to −30% after being subjected to the blister test procedure. [Aspect 10] 5. The composite film of embodiment 4, wherein the composite film exhibits a haze change of 0% to −21% after being subjected to the blister test procedure. [Aspect 11] 11. The composite membrane of any one of aspects 1 to 10, wherein the composite membrane comprises a plurality of ion exchange materials in the form of a mixture of ion exchange materials. [Aspect 12] 11. The composite membrane of any one of aspects 1 to 10, wherein the composite membrane comprises more than one layer of the ion exchange material, and the layers of ion exchange material are formed from the same ion exchange material. [Aspect 13] 11. The composite membrane of any one of aspects 1 to 10, wherein the composite membrane comprises more than one layer of the ion exchange material, and the layers of ion exchange material are formed from different ion exchange materials. [Aspect 14] 14. The composite membrane of claim 12 or 13, wherein at least one of the layers of ion exchange material comprises a mixture of ion exchange materials. [Aspect 15] 15. The composite membrane of any one of embodiments 1 to 14, wherein the ion exchange material is completely embedded within the microporous polymer structure. [Aspect 16] 15. The composite membrane of any one of embodiments 1 to 14, wherein the ion exchange material is partially embedded within the microporous polymer structure, leaving an unoccluded portion of the microporous polymer structure on an upper surface of the composite membrane. [Aspect 17] 17. The composite membrane of any one of embodiments 1 to 16, wherein the microporous polymer structure comprises expanded polytetrafluoroethylene. [Aspect 18] 17. The composite membrane of any one of embodiments 1 to 16, wherein the microporous polymer structure comprises a hydrocarbon polyolefin. [Aspect 19] 19. The composite membrane of embodiment 18, wherein the hydrocarbon material comprises polyethylene, polypropylene, or polystyrene. [Aspect 20] 20. The composite membrane of any one of embodiments 1 to 19, wherein the ion exchange material comprises at least one ionomer. [Aspect 21] 21. The composite membrane of embodiment 20, wherein the at least one ionomer comprises a proton conducting polymer. [Aspect 22] 22. The composite membrane of embodiment 21, wherein the proton conducting polymer comprises perfluorosulfonic acid. [Aspect 23] 23. The composite membrane of any one of embodiments 1 to 22, wherein the haze value of the composite membrane prior to said blister testing procedure is between 5% and 95%. [Aspect 24] 23. The composite membrane of any one of embodiments 1 to 22, wherein the haze value of the composite membrane prior to the blister testing procedure is 10% to 90%. [Aspect 25] 23. The composite membrane of any one of embodiments 1 to 22, wherein the haze value of the composite membrane prior to the blister testing procedure is between 20% and 85%. [Aspect 26] 26. The composite membrane of any one of embodiments 1 to 25, wherein no internal interfaces are formed within the layer of ionomer or between the coating of ion exchange material and / or the microporous polymer structure. [Aspect 27] 26. The composite membrane of any one of aspects 1 to 25, wherein the composite membrane comprises a single coating of the ion exchange material. [Aspect 28] 28. The composite membrane of embodiment 27, wherein the composite membrane has a thickness of 7 to 100 microns at 0% relative humidity. [Aspect 29] 28. The composite membrane of embodiment 27, wherein the composite membrane has a thickness of 17 to 50 microns at 0% relative humidity. [Aspect 30] 28. The composite membrane of embodiment 27, wherein the composite membrane has a thickness of 25 to 40 microns at 0% relative humidity. [Aspect 31] 28. The composite membrane of embodiment 27, wherein the composite membrane has a thickness of greater than 17 microns at 0% relative humidity. [Aspect 32] 27. The composite membrane of any one of aspects 1 to 26, wherein the composite membrane comprises a plurality of coatings of the ion exchange material, and wherein a first coating of the ion exchange material is formed over a second coating of the ion exchange material without subjecting the second coating to a drying step. [Aspect 33] 33. The composite membrane of embodiment 32, wherein the composite membrane has a thickness of 10 to 150 microns at 0% relative humidity. [Aspect 34] 33. The composite membrane of embodiment 32, wherein the composite membrane has a thickness of 15 to 80 microns at 0% relative humidity. [Aspect 35] 33. The composite membrane of embodiment 32, wherein the composite membrane has a thickness of 20 to 60 microns at 0% relative humidity. [Aspect 36] 36. The composite membrane of any one of embodiments 1 to 35, wherein the ion exchange material has an equivalent weight of 500 to 2000 g / mol equivalent. [Aspect 37] 36. The composite membrane of any one of embodiments 1 to 35, wherein the ion exchange material has an equivalent weight of 600 to 1500 g / mol equivalent. [Aspect 38] 36. The composite membrane of any one of embodiments 1 to 35, wherein the ion exchange material has an equivalent weight of 900 to 1200 g / mol equivalent. [Aspect 39] 36. The composite membrane of any one of embodiments 1 to 35, wherein the ion exchange material has an equivalent weight of 810 to 1100 g / mol equivalent. [Aspect 40] 40. The composite membrane of any one of embodiments 1 to 39, wherein the composite membrane is used in an electrochemical device to separate liquids contained within the electrochemical device. [Aspect 41] 40. The composite membrane of any one of embodiments 1 to 39, wherein the composite membrane is used in a redox flow battery. [Aspect 42] 40. The composite membrane according to any one of embodiments 1 to 39, wherein the composite membrane is used in a water electrolysis cell. [Aspect 43] A method of forming the composite membrane of any one of embodiments 1 to 31, comprising: (a) providing a support layer; (b) applying an ion exchange material to the support layer in one step; (c) obtaining a microporous polymer structure comprising at least one microporous polymer layer; (d) laminating said at least one microporous polymer layer to said ion exchange material to form an impregnated microporous polymer structure having a continuous ionomer phase; (e) drying the impregnated microporous polymer structure to form a composite membrane having a continuous ionomer phase; and (f) thermally annealing the composite film; A method comprising: [Aspect 44] A method of forming the composite membrane of any one of embodiments 32 to 35, comprising: (a) providing a support layer; (b) applying an ion exchange material to the support layer in one step; (c) obtaining a microporous polymer structure comprising at least one microporous polymer layer; (d) laminating said at least one microporous polymer layer to said ion exchange material to form an impregnated microporous polymer structure having a continuous ionomer phase; (e) applying said ion exchange material to the top surface of the impregnated microporous polymer structure according to method step (d); (f) laminating a second microporous polymer layer to the ion exchange material to form a multi-layer impregnated microporous structure having a continuous ionomer phase; (g) drying the multi-layer impregnated microporous structure to form a composite membrane having a continuous ionomer phase; and (h) thermally annealing the composite film; A method comprising: [Aspect 45] a cathode reservoir containing a positive electrolyte fluid; an anode reservoir containing a negative electrolyte fluid; and an exchange region comprising the composite membrane of any one of embodiments 1 to 41 disposed between a first side having a positive electrode and a second side having a negative electrode; Including, 1. A flow battery wherein the cathode reservoir is connected to a first side of the exchange area via a first pump and the anode reservoir is connected to a second side of the exchange area via a second pump. [Aspect 46] Obtaining a raw microporous polymer structure; applying an impregnating solution containing an ion exchange material to the untreated microporous polymer structure to form a treated microporous polymer structure having a continuous ionomer phase; and drying and thermally annealing the treated microporous polymer structure to form a composite membrane. wherein the ion exchange material forms a continuous ionomer phase within the composite membrane, and the composite membrane exhibits a haze change of 0% or less after being subjected to a blister test procedure.

Claims

1. 1. A method of forming a composite membrane, comprising: (a) providing a support layer; (b) applying an ion exchange material to said support layer in one step; (c) obtaining a microporous polymer structure comprising at least one microporous polymer layer; (d) laminating said at least one microporous polymer layer to said ion exchange material to form an impregnated microporous polymer structure having a continuous ionomeric phase; (e) drying the impregnated microporous polymer structure to form a composite membrane having a continuous ionomer phase; and (f) thermally annealing the composite film; comprising The composite film exhibits a haze change of 0% or less after being subjected to a blister test procedure, the blister test procedure comprising: In step 1, the composite membrane is immersed in a 6 mol / L aqueous sulfuric acid solution at 80°C for 3 minutes; In step 2, removing the composite membrane from the sulfuric acid aqueous solution; Step 3: immersing the composite membrane in deionized water at ambient conditions for 1 minute; In step 4, removing the composite membrane from the deionized water and repeating the cycle consisting of steps 1 to 4 at least twice; Step 5: drying the composite membrane at ambient conditions; and In step 6, counting bubbles or blisters formed on the composite film; A method comprising:

2. 10. The method of claim 1, wherein no internal interfaces are formed within or between layers or coatings of ionomer during the steps of applying the ion exchange material, laminating the microporous polymer structure, or any combination thereof.

3. The method of claim 1, wherein the drying and thermal annealing of the composite film is carried out at 160-220°C.

4. the composite membrane comprising a microporous polymer structure, and an ion exchange material at least partially embedded within said microporous polymer structure, rendering at least a portion of said microporous polymer structure occlusive; 2. The method of claim 1, wherein the ion exchange material forms a continuous ionomer phase within the composite membrane.

5. 10. The method of claim 1, wherein the composite membrane comprises a bottom surface adjacent the support layer and an opposing top surface on the opposite side of the composite membrane, and further comprises an additional layer of ion exchange material provided on the bottom surface.

6. The method of claim 1, wherein the haze value of the composite film prior to said blister testing procedure is between 5% and 95%.

7. 10. The method of claim 1, wherein the composite membrane having a continuous ionomer phase has a bubble or blister area of ​​less than 0.3% after being subjected to the blister test procedure.

8. The method of claim 1 , wherein the microporous polymer structure comprises expanded polytetrafluoroethylene.

9. The method of claim 1 , wherein the microporous polymer structure comprises a hydrocarbon polyolefin.

10. The method of claim 9 , wherein the hydrocarbon material comprises polyethylene, polypropylene, or polystyrene.

11. The method of claim 1 , wherein the ion exchange material comprises at least one ionomer.

12. The method of claim 11 , wherein the at least one ionomer comprises a proton conducting polymer.

13. The method of claim 12 , wherein the proton conducting polymer comprises perfluorosulfonic acid.

14. 2. The method of claim 1, further comprising, prior to step (e), applying an ion exchange material to a top surface of the impregnated microporous polymer structure from method step (d), wherein the impregnated microporous polymer structure has a bottom surface adjacent to the support layer, and the top surface is the surface of the impregnated microporous polymer structure opposite the bottom surface.

15. 15. The method of claim 14, wherein the ion exchange material is applied in step (b) to the top surface of the impregnated microporous polymeric structure without a drying step.

16. 15. The method of claim 14, wherein the step of applying ion exchange material produces layers of ion exchange material and no internal interfaces exist between the layers of ion exchange material.

17. 3. The method of claim 2, wherein the composite membrane comprises multiple layers of ion exchange material, one above the other, produced by the laminating step (d) or a subsequent step of applying ion exchange material, with no internal interfaces between the layers.

18. a cathode reservoir containing a positive electrolyte fluid; an anode reservoir containing a negative electrolyte fluid; and an exchange region including a composite membrane disposed between a first side having a positive electrode and a second side having a negative electrode; 1. A flow battery comprising: The composite membrane comprises: a microporous polymer structure, and an ion exchange material at least partially embedded within said microporous polymer structure, rendering at least a portion of said microporous polymer structure occlusive; Including, the ion exchange material forms a continuous ionomer phase within the composite membrane; The composite film has a haze, which is the ratio of diffuse transmittance to total transmittance of light passing through the composite film, and the composite film exhibits a haze change of 0% or less after being subjected to a blister test procedure, wherein the blister test procedure comprises: In step 1, the composite membrane is immersed in a 6 mol / L aqueous sulfuric acid solution at 80°C for 3 minutes; In step 2, removing the composite membrane from the sulfuric acid aqueous solution; Step 3: immersing the composite membrane in deionized water at ambient conditions for 1 minute; In step 4, removing the composite membrane from the deionized water and repeating the cycle consisting of steps 1 to 4 at least twice; Step 5: drying the composite membrane at ambient conditions; and In step 6, counting bubbles or blisters formed on the composite film; and 1. A flow battery wherein the cathode reservoir is connected to a first side of the exchange area via a first pump and the anode reservoir is connected to a second side of the exchange area via a second pump.

19. 20. The flow battery of claim 18, wherein the composite membrane is formed from multiple layers of ion exchange material disposed one above the other with no internal interfaces between the layers.

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